Fix errors when valuechange is delegated from a Widget.

Add delegate support to event-valuechange.

WIP on delegate support for valuechange. Fundamentally broken right now because we have no way of supporting more than one delegated subscriber on the same container node.

Rename the `valueChange` synthetic event to `valuechange`. All-lowercase is more consistent with DOM event naming. The old name will continue to be supported as an alias indefinitely for backcompat.

Pedantic style tweaks.

Use a native for loop for a slight perf increase.

Improve event-valuechange API docs.

API doc fixes and improvements.

Stop polling if the node disappears while polling.

API docs.

Use focus as an indication that we should start polling for changes. [Fixes #2529294]

Don't report stale changes that occurred while a node was not focused.

Argh. One more valueChange comment update. No code changes.

Replace API doc reference to "value-change" with "event-valuechange". Comment change only; no code changes.

Allow multiple subscriptions to valueChange on a single node. [Fixes #2529259]

event-valuechange performance improvements.

Rename value-change module to event-valuechange.